I've taken a lot of applicants out for dinner. And I personally don't care if an applicant drinks or not. Really, it's not a test. The same social "rules" about drinking apply as for any social situation. If you don't want to drink, simply say "no thanks" when offered. I probably wouldn't even notice. We always end up with a couple mormon applicants, and they don't drink, and like I said above, I usually don't even notice that they're not drinking. But if an applicant gave a preachy speech on the evils of alcohol and how we're all going to burn in hell for our moral turpitude in the middle of dinner... that I would notice.
On the other hand, if you do want a drink, and your hosts are drinking, or they offer you a drink, then order a drink and enjoy yourself. We wouldn't offer a drink if we were going to criticize you for accepting it after the fact. But again, use your social common sense. Don't drink if you can't hold your liquor. Don't have 5 drinks when the rest of us are having 2. Don't become obnoxiously drunk. Don't get all pretentious and demand expensive drinks if that's not what your hosts are ordering for themselves. Really, common sense stuff.
At our program, we usually take the applicants out to a bar/pool hall on Friday night, then after we are done with that, we take the applicants home around 11. But a couple students offer to take any applicant who wants to out for more bar hopping, dancing, etc. Because really, we want y'all to have fun and see what there is to do in the city. If you'd rather go back to the hotel, fine. Most do. But a few stay out late, and that's fine too. Applicants from both groups get into our program.